Most skylight leaks have nothing to do with the glass itself. The far more common cause is the flashing and sealant around the frame, the material that’s supposed to keep water from ever reaching the roof deck in the first place. When that seal breaks down, water finds its way in during a storm, even though the skylight unit itself is perfectly intact.
Flashing Fails Before Anything Else
A skylight is essentially a hole cut into your roof, and the flashing around it is doing all the real work of keeping that hole watertight. Flashing is metal, and metal expands and contracts with temperature swings all year, which loosens fasteners and opens tiny gaps over time. In New Jersey and Pennsylvania, that cycle runs hard, hot summers into cold winters, and it’s usually the flashing, not the skylight, that gives out first.
Is It a Leak or Condensation?
Not every drip is a leak. Warm, moist household air hits the cold glass of a skylight on a cold morning and condenses, then drips down the frame and looks exactly like a leak to someone standing underneath it. The difference usually comes down to timing. Condensation shows up on cold, clear mornings regardless of weather. An actual leak shows up during or right after rain or melting snow. If you’re only seeing moisture after a storm, that points to the flashing or sealant, not the glass.
What to Check Before Assuming the Worst
Look at the sealant around the frame from inside the attic or crawlspace if you can safely get to it. Cracked, shrunken, or missing caulk is a visible sign the seal has failed. From the roof, a visual check for lifted or corroded flashing, especially on the uphill side of the skylight where water runs against it, often finds the source before anyone gets on a ladder to test it.
When It’s Bigger Than the Skylight
Sometimes a skylight “leak” is actually a symptom of a roof problem nearby, like a failing section of shingles or underlayment uphill from the skylight sending water toward the frame instead of past it. Re-sealing the skylight alone won’t fix that. It just delays the same water finding a different way in next season.
Getting It Actually Fixed
We handle skylight leaks as part of our regular roof repair work across NJ and PA, and we check the surrounding roof section at the same time so we’re not just patching the symptom. If you’ve got a skylight that drips during storms, call Warren Thompson & Son at (908) 774-9229 for a free inspection. If a storm has already gotten the better of it, call us right away.
